[iOS] Enable InvitationCppTest unittests in //mojo

If 'use_blink' is true, this CL enables InvitationCppTest
on iOS in //mojo with disabling NamedPlatformChannel test
code. iOS port needs to check if NamedPlatformChannel can
be supported.

Bug: 1418597
Change-Id: Ic3d07a458b2cb2f579e67e9f53a13d9e71f19f3f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4344669


Reviewed-by: Ian Vollick <vollick@chromium.org>
Commit-Queue: Gyuyoung Kim <gyuyoung@igalia.com>
Reviewed-by: Ken Rockot <rockot@google.com>
Cr-Commit-Position: refs/heads/main@{#1118443}